1. Field of the Invention
The present invention broadly relates to techniques for clamping various types of structures during manufacturing thereof and, more particularly, is concerned with a pneumatic device for clamping parts of structures together while fastener holes are drilled through the structures.
2. Description of the Prior Art
Several approaches are disclosed in the prior art for clamping various structures, such as a pair of metal sheets, together. One approach employs a clamping mechanism 10 comprised by a collet 12 and a mandrel 14 shown in FIG. 1 which is used in conjunction with and as an integral part of a machine assembly called a drillmotor (not shown). The collet 12 must be inserted through a previously drilled hole to a depth so that the flanges 16 at the base of the collet are through the hole. A clamping force is applied when the tapered mandrel 14 is drawn upward into the slotted section of the collet. The force exerted by the mandrel 14 spreads the collet 12 to fill the hole and presses upward so that the collet flanges 16 bear against the lower surface of the part through which the collet was inserted. One such device is manufactured by Omark Industries and is known as a Spacematic Drillmotor.
Another approach utilizes a hand operated mechanical clamping device which exerts varying degrees of clamping force depending upon the torque applied to the device. This device is commonly referred to as a "cleeco" clamping device. Patents to Finkle, U.S. Pat. No. 2,280,403; Rossman, U.S. Pat. No. 2,371,470; Mooy, U.S. Pat. No. 2,388,603; Van Sittert, U.S. Pat. No. 2,397,892; Cole, U.S. Pat. No. 2,561,098; and Jones, U.S. Pat. No. 3,096,679, show clamping devices of the "cleeco" type.
Several disadvantages are inherent in these existing clamping approaches and deleterious effects result therefrom. The size of the collet and drillmotor assembly plus a template foot and tail pad which are integral parts of the assembly make the assembly unwieldly and restrict use of the assembly to large, open and uniformly contoured surfaces. An additional disadvantage to this device is that the collet grip ranges are limited and collets must be changed as various thicknesses of material are encountered during assembly operations. Disadvantages to the "cleeco" device are that the mechanical operations for its installation and removal are time consuming. Also, in most instances the device is not capable of applying a constant clamping force and frequently must be retorqued after initial installation to apply desired clamping force. A further disadvantage to the "cleeco" device is that the small footprint provided by this device at the point where the clamping force is applied to the understructure can inflict damage to the understructure if the "cleeco" device is overtorqued.
Therefore, a need exists for an improved device for clamping structures together which is easy to handle, has substantially universal application in not being limited by the shape of the structures, and will quickly and simply provide a constant, controlled clamping force.